When the metabolic activity is important and/or when humidity and temperature conditions are difficult it is necessary to bring an active cooling to the subject.
Many systems exist allowing the transfer of cooling energy to a subject.
The patent FR-26 19 315 dated Feb. 17, 1981 concerns a garment maintained under light pressure by a gas, for example CO2, contained in a container under pressure. It does not allow cooling of the subject efficiently.
The patent EP-03 48 835 A2 of Jan. 3, 1993 concerns a garment protecting against accelerations comprising a fluid capable of transporting cooling energy circulating through a heat exchanger. The presence of a different fluid and a heat exchanger induces global losses and added supplementary costs.
The patent WO 91 04 722 A1 of Apr. 18, 1991 concerns a device for cooling of a body by evaporation of liquid on the external face of the garment. It does not allow cooling of a subject placed inside a seal tight garment, or in an humid atmosphere.
The patent EP 057 0301 A1 of Nov. 18, 1993 concerns a device that destroys body cells by applying ultra cold substances. This device does not allow cooling of a human being.
The patent EP 04 90 347 of Jun. 17, 1992 concerns a vest placed at some distance from the skin and comprising a ventilation of air allowing cooling of the subject. This system does not allow cooling of the subject when the air is hot and humid.
The patent FR 27 06 740 of Dec. 30, 1994 concerns a refrigerant composite material whose functioning is based on a chemical reversible reaction between a solid and a gas. This system is not effective and very heavy.
The patent FR 26 21 459 of Apr. 14, 1989 comprises a source of cooling energy packed and supplied by an elastic opening system. This system does not allow a cooling of the homogeneous body and is not adaptable.
The company DRAEGER has proposed a cooling system based on carbon dioxide comprising a fluid (oil and silicone based) moved by a pump making the fluid pass successively in the garment and in a heat exchanger placed near the solid block of carbon dioxide. The utilization of oil and silicone based fluid that solidifies at very low temperature introduces problems and generates extra costs and performance losses that increases the mass of the pump and batteries. This solution is unusable since it leads to a system having a mass and cost way above potential users expectations.
The company INTERTECHNIQUE has proposed a solution using liquid air placed in a reservoir and cooling the subject using a heat exchanger. This solution leads to a very heavy system, dangerous and very expensive.
The French patent no. 98 05 374 allows to realize some blocks? every day on site but do not solve the problem to have an efficient and usable complete system for a great number of individuals displaced in operation.
The French patent no. 95 15 234 is a portable system comprising a reservoir under pressure. This reservoir has to be leak tight and resistant to internal pressures. It is therefore, heavy, more expensive and dangerous.
None of the solutions proposed in the past allows one to realize a simple, light, safe, and economical system.
In fact it can be noticed that it is very difficult to cool a human being because the skin is at about 34 degrees Celsius approximately and does not tolerate the contact of too low temperatures.
The utilization of the cooling power coming from the sublimation of solid carbon dioxide has necessitated many tests, but has now lead to the realization of an effective prototype.
The present invention aims to provide a system allowing to cool one individual or several persons efficiently, in comfort and for a minimal mass and a minimal cost.
The carbon dioxide, during sublimation, liberates an important cooling energy (627 kilojoules by kilogram). This cooling energy can be used efficiently to cool a subject that is too hot. The fundamental problem is the optimal transfer of this available cooling energy to the human bodies while respecting the physiological limits of the human body.
A goal of the invention is to realize a complete system allowing the comfortable and efficient cooling of one or several individuals, this system being light, portable, safe and having a low operating cost.
These goals are achieved by the individual cooling system, according to the invention comprising:
at least a garment V worn near the body comprising several fine pipes in which circulates a fluid carrying the cooling energy and solidifying at the temperature TF and bringing the cooling energy to the subject, this garment having characteristics of pressure drop as a function of the flow following the relation
D=F1(PExe2x88x92PS)
Where D is the flow of the fluid in the garment
PE is the pressure at the entry of the garment
PS is the pressure at the exit of the garment
F1 is the function that links the flow and the pressure drop of the garment
at least a thermally insulating container containing a substance liberating a quantity of cooling energy QE by phase change at a temperature TCP and containing a heat exchanger E2 having the following characteristics of flow as a function of pressure drop:
D=F2(PCxe2x88x92PF)
Where
D is the flow of fluid carrying the thermal energy
PC is the fluid pressure at the container entry
PF is the fluid pressure at the container exit
F2 is the function that links the flow and the pressure drop of the container
at least a pump P moving the fluid carrying thermal energy in the circuit E1 of the garment V and in the heat exchanger E2 of the container, this pump having the following characteristics of flow as a function of differential pressure:
D=F3(PFxe2x88x92PA)
Where
D is the flow of the fluid carrying thermal energy in the pump P
PA is the pressure at the entry of the pump P
PF is the pressure at the exit of the pump P
F3 is the function that links the flow and the differential pressure of the pump P
characterized by the presence of at least a device allowing the continuous functioning in of the system without solidification of the fluid carrying the thermal energy, although the temperature of solidification TF of this fluid is superior at least by more than 10 degree Celsius of the temperature of the block B of substance liberating the cooling energy by phase change.
It is advantageous that one of the said devices comprises an assembly of walls, constituting the heat exchangers E1 and E2, having thermal characteristics calibrated in function of characteristics of the pump P and pressure drop of circuit of the garment and the container, in such a way that the coefficient K1 is three to ten times superior to K2 where
K1=s1/((e1)(ct1))
where
s1 is the surface of exchange of the heat exchanger E1
e1 is the thickness of walls of the heat exchanger E1
ct1 is the thermal exchange coefficient of the material constituting the heat exchanger E1
and where
K2=s2/((e2)(ct2))
where
s2 is the surface of exchange of the heat exchanger E2
e2 is the thickness of walls of the heat exchanger E2
ct2 is the thermal exchange coefficient of the material constituting heat exchanger E2,
in order that the fluid carrying the thermal energy, in normal use, never reaches its solidification temperature while allowing a satisfying transfer of the cooling energy from the block to the human body.
It is advantageous that said heat exchanger E2 comprises a circuit where the pipes are placed in such a way that the fluid at low temperature and the fluid relatively warmer having circulated in the vest are placed side by side so that the average local temperature is as constant as possible at every point of the heat exchanger.
It is advantageous that the fluid carrying thermal energy is a mixture of water and antifreeze having an solidification temperature equal to xe2x88x9235xc2x0 C. while the carbon dioxide contained in the container is at a temperature equal to xe2x88x9278xc2x0 C.
It is advantageous that said container is placed in a vehicle comprising
a quick connector for connecting and disconnecting the vest from the container
a device allowing the fluid carrying the thermal energy not to solidify in case of disconnection.
It is advantageous that the said device allowing the fluid carrying the thermal energy not to solidify in case of disconnection, comprises a circuit in parallel comprising
a valve having a threshold of opening between 0.25 bar and 1 bar
an heat exchanger allowing to evacuate automatically the excess cooling energy
It is advantageous that a means of adjustment allows the subject wearing the garment to regulate the cooling power that is brought to him.
It is advantageous that said adjustment is a faucet placed in the circuit of the garment allowing one to increase the pressure drop of main circuit and thus to distribute flows part for the vest and part for the secondary circuit.
It is advantageous that at least two garments carried by at least two subjects are placed in parallel on the circuit and each one comprises an independent adjustment means of flow and therefore cooling power according to the desire of each subject and this is accomplished using only one container.
It is advantageous that the gas coming from the sublimation of the block is sent preferentially on the internal part of a visor so as to demist it.
It is advantageous that the gas coming from the sublimation of the block is used to reduce the oxygen partial pressure of the gas constituting the confined atmosphere of a seal tight suit.